I have a 1988 Chevy Van and have installed a recently rebuilt 305 Roller cam engine in it with the early vortex type cast iron heads...it runs great ! It Ran 20,000 miles with the 60 lbs oil pressure gauge right at the top about 58 lbs I would say on the gauge ...This was Even at idle ! ...NOW in the last 4 thousand miles the pressure is dropping rapidly and is about 20 pounds on the gauge at 60 MPH and down to 10 pounds at idle it is barely into the acceptable range just above the red mark on the gauge at idle ...Is there a common problem with these engines that causes this sort of problem something that fails often ? Could it be the gauge ? or sender ? What is the most likely to cause this ? You can email me direct at
W8MDV@yahoo.com if you want or post a reply here...THANK YOU IN ADVANCE ! Bob 1942

Double check the oil pressure with a known good gauge. If it echoes what you are seeing on the dash gauge, then you might have a bearing issue. Who did the work on the engine? Has this engine been overheated?

This is not normal behavior.

Thanks for your reply ... No the engine has not been overheated ... I did the engine work myself with help from a good well known engine machine shop They do racing engines they did the stuff I was not equipped to do like bore the block and check all the crank shaft journals ...I checked all bearings with plastigauge when I assembled the engine and all of them were within new engine limits ...I used all new good quality parts ...Your right I really need to check the oil pressure with a good test gauge to show if it is really a low oil pressure problem or a bad sender or gauge ... Right now it is 20 degrees out there so it will have to wait awhile ... BOB




Double check the oil pressure with a known good gauge. If it echoes what you are seeing on the dash gauge, then you might have a bearing issue. Who did the work on the engine? Has this engine been overheated?

This is not normal behavior.

Thanks for your reply ... No the engine has not been overheated ... I did the engine work myself with help from a good well known engine machine shop They do racing engines they did the stuff I was not equipped to do like bore the block and check all the crank shaft journals ...I checked all bearings with plastigauge when I assembled the engine and all of them were within new engine limits ...I used all new good quality parts ...Your right I really need to check the oil pressure with a good test gauge to show if it is really a low oil pressure problem or a bad sender or gauge ... Right now it is 20 degrees out there so it will have to wait awhile ... BOB
Love those Chevy vans..... I have owned 3 of them......

I put a decent aftermarket mechanical oil pressure gauge in mine. They are easier to install and more accurate than an electric. It's easy and you can do it while sitting in the driver's seat (it's warmer). You do not have to crawl underneath the truck.

Remove the 'dog-house' engine cover. You should find the original oil pressure sender near the distributor. I used a little brass 'tee' fitting so I retained the original sender as well as installed the new one.

As for the loss of pressure......... did you use new bearing cap and oil pump bolts? I have often re-used bolts without a problem, but sometimes old bolts have been overtightened or stretched past their 'yield' point. This means the bolt has become weakened. When assembled, they will hold their torque properly but will loosen up over a few weeks or months of use and eventually fall out.
It could also be just the oil pump bolts are loosening up or the pick-up tube has become loose or blocked.
Also the oil pressure relief valve spring may have broken or come loose.